The present invention relates to a novel method and system for treating wellhead gas to recover valuable liquefiable hydrocarbon components from such gas and for utilizing the resulting dry gas as a fuel for internal combustion engine-generator systems for the co-generation of electric power.
Wellhead gas is generally comprised of a mixture of the following gases and vapors: nitrogen, carbon dioxide, methane, ethane, propane, iso-butane, n-butane and iso-pentane; and small quantities of entrained water, all obtained as by-products of gas and oil field production operations at the well heads. Wellhead gas is particularly rich in methane gas (75-95 mol %), includes appreciable quantities of ethane (3-8 mol %) and propane (0.5-5 mol %), and as a moisture-free mixture has a heating value of 1400-2000 Btu per cubic foot. For new gas or oil wells the utilization of wellhead gas has a rather low economic attractiveness because of the relatively low quantity of such gas with respect to the high value gas and liquid petroleum products directly produced from such new wells. As wells mature the utilization of wellhead gas is an increasingly important factor in the economic decision to continue gas and oil production.